1. Field of the Invention
The invention relates to a contact element having contact points for the electrically conductive connection of contact regions of mutually spaced elements, for example circuit boards. The invention also relates to a method for the manufacture of such a contact element as well as a contact device which comprises a plurality of such contact elements.
2. Description of Related Art
Contact elements of the generic type are for example used to form so-called board-to-board (B2B) connectors, by means of which two circuit boards arranged at a distance from one another are connected in an electrically conductive manner.
The contact elements should thereby ensure an as far as possible loss-free transmission of the radio frequency signals, including within a defined tolerance range in terms of parallel alignment and spacing as well as any lateral offset of the two circuit boards or their contact regions. Further requirements are economical manufacture and simple assembly. In addition, the axial and radial dimensions of the contact elements should be as small as possible, since the continuing further miniaturization of circuit boards and the circuit traces applied to them means that the number of contact elements which need to be arranged next to one another within a limited space is increasing all the time.
It is known for a connection between two circuit boards to be established by means of two coaxial plug connectors permanently connected with the circuit boards together with an adapter connecting the two coaxial plug connectors, the so-called “bullet”. This adapter makes possible a compensation of axial and radial tolerances, as well as the compensation of parallel alignment tolerances. Typical coaxial plug connectors used for this purpose are SMP, Mini-SMP or FMC.
Alternatively, electrical connections between two circuit boards are also realized by means of spring-loaded contact pins in individual conductor and/or multiple conductor design. Such spring-loaded contact pins comprise a sleeve and head which is partially guided within the sleeve as well as a helical spring which is supported between the head and the sleeve. The properties required of the helical spring in terms of spring force and block length demand relatively long spring lengths, which have a correspondingly disadvantageous effect on the axial construction height of the spring-loaded contact pins.
A coaxial contact element is also known from U.S. Pat. No. 6,776,668 B1 by means of which radio frequency signals are to be transferred between two circuit boards. An inner conductor, which is designed in the form of a spring-loaded contact pin, serves as a signal conductor, while an outer conductor surrounding the inner conductor performs the function of a return conductor as well as acting as a shield for the inner conductor. The outer conductor comprises a sleeve-formed base body which is split several times in the longitudinal direction. The unsplit end of the base body forms on its end face a contact point for making contact with a contact region of one of the circuit boards. A sleeve of the outer conductor is guided displaceably on the base body and forms on one end face a contact point for making contact with a contact region of the other circuit board. A pre-tensioned spring is supported between the base body and the sleeve. When the two circuit boards are connected, both the head of the inner conductor and the sleeve of the outer conductor are displaced, with further tensioning of the relevant springs, as a result of which a more reliable contact pressure can be provided, despite possible tolerances in terms of the distance between the contact regions of the circuit boards. In addition, the splitting of the base body means that this also possesses a certain flexibility in a lateral direction, which is intended to ensure that even relatively large deviations in parallel alignment between the two contact regions can be compensated.
Fundamentally, the known contact elements have relatively large dimensions, which, moreover, as a result of their construction design and the resulting function, cannot be reduced indefinitely. For example, a reduction in the diameter of plug-socket connections such as are used, inter alia, in the aforementioned SMP plug connectors, is only possible up to a certain limit, since otherwise with the materials usually used problems would arise with regard to the strength of plug and socket, in particular when plugging together the plug connection.